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The satellite was tracked by observatories around the world, forming the first stage of the now vitally important global positioning system (GPS) that is used for all kinds of modern surveying and direction finding.
The position of the satellite was found by its Doppler effect, caused by its movement. As the satellite sped away from the observing station, its signal frequency changed in one direction, while as it moved toward another station, its signals appeared to change in the opposite direction.
On November 3, 1957, Sputnik 2 was put into orbit before a now awestruck world. It weighed 508.3 kg and carried the first living creature—a dog named Laika— into space.
Sputnik 1
 Sputnik 1 (PS-1) was launched on October , 1957. It was the first human-made object in space. Developed
in November 1956, it was launched when the original ambitious plan for a more complex satellite was shelved in favor of beating the Americans to get the first object in space.
The pressurized sphere— named Sputnik, or Satellite— was made of aluminum alloy and designed to test the method of placing an artificial satellite into Earth orbit, to provide information on the density of the atmosphere,
to test radio and oPTical methods of orbital tracking, to examine the effects of radio waves moving through the atmosphere, and to check principles of pressurization used on the satellites.
To do this, it used temperature sensors pressurized with nitrogen gas. Changes in temperature caused changes in the signals sent to Earth. At the same time, the nature of the radio signals as they traveled to the Earth gave important information about the ionosPhere.
Sputnik was powered by internal batteries, and so its signal stopped when the batteries ran out 21 days after launch.
Find about more about the global positioning system in Volume 8: What satellites see.
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